Method of making refractories



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METHOD OF MKING REFRCTORES Filed Feb. 27, lQZ

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Patented May l, 1934 UNITED STATES PATENT OFFICE METHGD F MAKINGREFIEACTORIES a corporation of Ohio Application February 27,1932, SerialNo. 595,579

8 Claims.

This invention relates to refractories for hot tops, and has referenceparticularly to the chemical constituents of such refractories and themethod of producing the same. The refractories which are the subject ofthe invention may be employed for the production directly of hot topseither as unitary or built-up assemblies, or they may be employed aslining elements for metal casings or frames. 4

One of the objects of the invention is the provision of a refractory ofthis character which shall be economical to produce, and one which canbe formed with a relatively high degree of accuracy in comparativelylarge units, the large units facilitating the assembly of' the hottop orits reconditioning after use.

Another object is the provision of a hard rigid refractory which shallbe resistant to deterioration during storage and capable of withstandingrough handling in shipment.

In the drawing:

Figure 1 is a perspective View looking downwardly upon a one-piece lowerlining ring for a hot top, this ring being formed of the composition ofmatter and by the method of the present invention.

Fig. 2 is a transverse sectional view of the same taken substantially onthe line 2-2 of Fig. 1, thereby showing the ring in an invertedposition.

The ring illustrated in the drawing is merely one example of a hot toprefractory which may be formed of the composition and by the method ofthe present invention. Complete hot tops consisting of refractorymaterial alone may be built up of a plurality of molded elements, or insome cases may be molded as a unitary structure employing the presentcompositionn and method, and Where a metal casing orframe is employed itmay be protected by means of a refractory' lining in one or a pluralityof pieces formed or" the composition and by the method of thisinvention. The ring herein illustrated constitutes one element of alining for a hot top casing, being intended to be used as a substitutefor a lower lining course formerly constructed of a plurality ofrefractory blocks, such for instance as those illustrated in Patent1,804,206 to Charman et al, dated May 5, 1931.

In the drawing the ring 10 is a homogeneous, one-piece structure havinga perimeter formed with a contour corresponding with the inner contourof the ingot mold with which the hot top is to be used. Along its inneredge the ring is formed with an upstanding rim 1l which is adapted toprotect the inner edge of the casing ledge,

by means of which the other lining elements of the hot top aresupported. It also aords a means for centering the ring on the hot top.Any suitable means may be employed for attaching the ring 10 to thecasing, holes 12 being provided in the present instance for thereception of Wire ties.

The ingredients whichwe employ in making up these refractories include asuitable aggregate that is free from any impurity that will reactchemically in a harmful manner with the binder, and one in which theparticles are of suitable size, The size of particles should be suchthat the resulting article is dense enough to have considerablestrength, and yet not too dense to prevent any vapors or gases, set freeat the time the metal is poured, from Venting ofi". The aggregate whichWe prefer to employ is silica sand of a relatively ne grade, washed toremove any impurities.

While it is possible to employ various binders with diierent degrees ofsuccess, we have discovered after extensive experiments that by far thebest results are obtained, particularly with silica sand as theaggregate, from the use of sodium silicate. This is employed preferablyin solution. and although the moisture content may be varied more orless, we prefer to employ one containing 36.47% solids and 63.53% water.To produce the maximum adhesive strength of sodium silicate the ratio ofsodium oxide to silicon oxide should be approximately one to three. Anymaterial deviation from this ratio will cause a marked decrease inadhesiveness. For reasons of manufacture, and to obtain the properphysical condition, we prefer to use sodium silicate having a ratio ofone to 3.25. As the alkalinity of sodium silicate increases the waterresistance decreases quite rapidly. The quantity of silicate solutionwhich should be used may be varied within workable limits, the maxium ofwhich would be twenty percent by weight.

The amount of moisture in the batch isof a high degree of importance.For example, when the aggregiate and binder used are as above stated,the added water content may be varied only within the small limits ofthree-tenths percent to one percent by weight of the whole mass, theproportion depending somewhat upon the screen analysis of the sand andto a slight extent also upon the exact character of the silicate. Whenthe batch is too dry it is extremelyl difficult to ram it properly orotherwise compact it within the mold, Whereas if too much moisture isemployed the compound sticks to the mold box bad- .one percent by Weightof the whole mass.

ly and it becomes impossible to turn out a perfectly formed article.

One of the requisites of a good commercial refractory for hot tops isthat it shall satisfactorily withstand hard usage, particularly inshipment, and shall remain hardand rigid after being exposed to theatmosphere for a considerable time, as when stored in an unprotected ordamp place. We have found that the refractories in question may berendered practically permanent regardless of atmospheric conditions byincluding in the mixture from which they are molded a certain quantityof the oxide of some metal, preferably zinc or lead. Aluminum oxide issuitable for the purpose, but on account of its greater cost, we preferto employ instead either zinc or lead oxide. Although the amount of thiswater-proofing agent may be increased to some little extent, theproportion which we have found sufficient is Less than five-tenths wouldbe too little to be effective, and more than five percent would increasethe cost of the article Without corresponding benents.

A metal reenforcement of any suitable form is desirable but notessential. A steel rod for this purpose is indicated at 13 in Fig. 2 ofthe drawmg.

Referring now to the method of making the refractories, the sand and thezinc or lead oxide are rst mixed in any suitable type of mixer untilthey are thoroughly blended. The sodium silicate and the Water are thenadded and the mixing is continued until the entire batch has becomeuniform. The mold is then coated with some suitable material, as forinstance lycopodium, toform a good parting surface. The mixture isplaced in the mold and compacted by ramming or otherwise., When therefractory is thus molded, it is placed in anroven and dried by bakingit at a fairly high temperature, that is to say at a maximum of 500 F. Asomewhat lower maximum is preferred however, say between 375 and 425 F.It should be further understood that somewhat lower temperatures couldbe used, and the drying time lengthened accordingly, without affectingthe quality of the product. The drying should be done in an atmospheresubstantially free from carbon monoxide and carbon dioxide, as forinstance in an electric oven or in a munie type oven. If a substantialamount of carbon monoxide or carbon dioxide is present the silicate isconverted to a carbonate and loses the attributes of a binder, with theresult that the article crumbles and has no strength. been found that ifthe oven temperature exceeds 500 F., and such high temperature ismaintained for any considerable period of time, an excessive loss ofmoisture will result, and the bonding qualities of the silicate will beimpaired to a greater or lesser extent. Also, if the refractories arecooled too rapidly they will crack. On the other hand, if they areheated up too rapidly at the beginning of the drying operation, thesilicate on the surface will dry and harden very quickly and will retardthe escape of water vapor from the interior of the refractory. This maycause bulging and warping. 'We have therefore determined that in thedrying operation the oven heat should be increased slowly until a givenhigh It has temperature is reached, and that when the drying issubstantially completed the temperature of the refractories should belowered very gradually preferably until normal room temperature isreached. l

Having thus described our invention, we claim:

1. The method of making refractories which consists in thoroughlycommingling sodium silicate solution and an aggregate chemically inertto sodium silicate, compacting the mixture, and baking it in anatmosphere substantially free from carbon monoxide and carbon dioxide ata temperature no greater than 500 F.

2. The method of making refractories which consists in thoroughlycommingling sodium silicate solution and silica sand, compacting themixture, and baking it in an atmosphere substantially free from carbonmonoxide and carbon dioxide at a temperature no greater than 500 F.

3. The method of making refractories which consists in thoroughlycommingling an aggregate chemically inert to sodium silicate with asodium silicate solution having an alkalinity approximating one part ofsodium oxide to three and one-fourth parts of silica, compacting themixture, and baking it in an atmosphere substantially free from carbonmonoxide and carbon dioxide at a temperature no greater than 500 F.

4. The method of making refractories which consists in thoroughlycommingling sodium silicate solution and silica sand, adding moisture tothe extent of three-tenths per cent to one per cent of the whole byWeight, compacting the mixture, and drying it in an atmospheresubstantially free from carbon monoxide and carbon dioxide.

5. The method of making refractories comprising as ingredients sodiumsilicate solution, a metal oxide, and an aggregate chemically inert tosodium silicate, the sodium silicate solution being present in a maximumproportion by weight of twenty percent and the metal oxide being presentin proportion by weight of approximately fivetenths percent to vepercent, which consists in thoroughly commingling the aggregate with themetal oxide, adding the sodium silicate solution, remixing, compactingthe mixture, and baking it in an atmosphere substantially free fromcarbon monoxide and carbon dioxide.

6. The method of making refractories which consists in thoroughlycommingling sodium silicate solution and an aggregate chemically inertto sodium silicate, compacting the mixture, and baking it in anatmosphere substantially free from carbon monoxide and carbon dioxide.

7. The method of making refractories which consists in thoroughlycommingling sodium silicate solution and silica sand, compacting themixture, .and baking it in an atmosphere substantially free from carbonmonoxide and carbon dioxide.

8. The method of making refractories which consists in thoroughlycommingling an aggregate chemically inert to sodium silicate with asodium silicate solution having an alkalinity approximating one part ofsodium oxide to three and onefourth parts of silica, compacting themixture, and baking it in an atmosphere substantially free from carbonmonoxide and carbon dioxide.

WALTER M. CHARMAN. PHILIP R. WARD.

